Chriske
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Posts posted by Chriske
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Some progress ...
Mount not finished yet
Upper polar axis, threaded rod M16
Lower polar axis, brass axis 12mm
Movement...
Still... drive unit + motor to be installed.
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Today the secondary mirror will be installed
It has a diameter of 800mm, Also gold coated.- 1
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The mirrors are a bit deformed because we have tilted the complete set 15° forward.
When the mirrors will be relocated to it's final destination all will be installed perfectly vertical and the deformations will disappear.
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Btw the curly boy in the mirror's reflection holding the camera is me. In real I am not that curly...😁
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A few more changes.
The two red axis are both fixed. They will be connected by a GT2 belt or maybe a set of gears don't know yet.
The cycloidal drive has a reduction of 15x
For quick adjusting the polaraxis I'll add a green laser parallel to the upper polar threaded rod.- 3
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To be more flexible I'll drop the bevel gears and replace it with a stepper and a Cycloidal Drive.
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Not yet started building.
A few changes have been applied, has to do with the tracking speed.
Instead of bevel gears I'll be using a Worm/wormwheel set. -
I already made a JWST scale model 1:7...😉
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Just now, Dr_Ju_ju said:
My one suggestion would be to cross-grain the timbers to reduce the amount of wooden flex in differing temperatures etc....
👍
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Change of plan : Plan 'C' is to buy sheets of acrylic that has a 'standard' glossy gold finish on it's surface.
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A long time ago I saw something similar.I kept working on it and came up with this solution to track the stars with a Dob.
I added a tracking system based on a few cardan couplings and a thick threaded rod.
In the thick wooden beams I added a few rods @51°(polar axis), both in the vertical as well in the horizontal beams. All will be supported by ball bearings.
These bearings are all sitting in a printed blocks.
Tracking is done with a small motor and two bevel gears.
Running time of the unit is about 90minutes.
Next week I'll start building one.- 5
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On 12/06/2024 at 12:55, Owmuchonomy said:
We have an animation which resolves into a full scale image of the JWST primary and secondary mirror onto the dome. This usually creates some gasps across the audience when they grasp the unfolded size.
Wooow...! Nice idea...!👍
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First test were very disappointing.
Using 3mm plywood resulted in very bad surface quality, Even after applying a few coats of varnish.
The idea was (after varnishing and sanding) to add a layer of (high)glossy gold vinyl.
So now plan 'B' is to use sheets of acryl. Acryl has a very flat surface. Did already a small test and it looks promising.- 4
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Just started building a full scale model of JWST's mirror.
It will be the show-piece of our next open door at our observatory mid September.
Yep, that thing is 6.5m high...Now that I come to think of it, I should not use the word 'scale' but rather 'copy'...😄
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I did replace that blue filter and made a very big difference. The old one became somewhat foggy.
In my case it was a Lunt. -
We often shared files, Gina and myself
Gina's giant clock was one of here favourite projects. She printed it on here 'Giant printer'.
She sent a copy of here clock(she drew it her self..!!) to me. If I'm not mistaken it has a diameter of nearly 500mm
It used a small stepper... -
You're going to enjoy this big bino. Observing with these large binos has many advantages. Simply said, you see much more compared to a 'singles scope'. I've built a few binos myself...😉
To me, as a mechanical engineer, there's a high drooling factor involved in what you construct...👍
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Thanks John,
Nice tool..!
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David,
I'll be using that 'Plossl' in combination with a 150mm refractor f15.7.
So primary image of the Sun will be about 24mm. I'll project the image of the sun on a white screen. I'll be refocusing until I have a very large sun on that screen.So if the combined FL of that Plossl is 90mm it has no effect on the projected image. Visual observing would indeed give me a very low magnification. But I will not use it for visual observing at all.
The most important reason why I use these large lenses, and as a Plossl combination, is to avoid heating up that eyepiece while projecting the sun.
Thanks for the input. Still have to learn about these self-made eyepieces...;-)
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Did not know where to post, so I also posted in the eyepiece section.
Hi,
Just finished building an eyepiece and I was surprised it worked, and it worked rather good as a matter of fact. It was a quick test using a refactor with a 1 1/4 focuser, handhelding that eyepiece. So I could not see the entire FOV.
From what I've read the acromats should be placed as near as possible, front lenses pointing to each other, so I did.
I made a holder in which I could change the spacing between the two. Observed a large post at about 300m distance : in both occasions, lenses very near and also at about 60mm apart the result is just the same.
How is that possible...?
Lenses 50mm diameter(was a binocular) F=180mm
Thanks...
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Just finished building an eyepiece and I was surprised it worked, and it worked rather good as a matter of fact. It was a quick test using a refactor with a 1 1/4 focuser, handhelding that eyepiece. So I could not see the entire FOV.
From what I've read the acromats should be placed as near as possible, front lenses pointing to each other, so I did.
I made a holder in which I could change the spacing between the two. Observed a large post at about 300m distance : in both occasions, lenses very near and also at about 60mm apart the result is just the same.
How is that possible...?
Lenses 50mm diameter(was a binocular) F=180mm
Thanks...
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Done and ready to use it in two ways...
This position is to observe..
and this is the 'other' position...😀
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Optically it performs rather good, as a matter of fact I was a bit surprised.
To be clear it is not a optical masterpeace, I made 'a few' better mirrors in my lifetime.
Visitors at our open door will not see the difference between a perfect 'bottle' and mine...😉Problem during polishing and figuring a square @ f/4 (about) there's no ideal way of polishing a square mirror on a circular lap. Or is it...?...😄
Wooden equatorial platform
in DIY Astronomer
Posted
Forgot to mention. In the most upper (printed) part there's room for a laserpointer to align the unit to the north.
In that part the hole for the major (M16) bolt and the hole for the laser are printed in one piece, so I can set it up very accurately.
The laser is adjusted in a lathe.